Device for transporting magazines for molding wafer-shaped objects

ABSTRACT

The object of a device for transporting magazines for holding wafer-shaped objects is to ensure an exchange of gases within a SMIF box to the required extent at low cost and in an effective manner with respect to time in conformity to the working regimen associated with an SMIF system. A gas feed duct proceeding from closable ducts incorporated in the wall opens into gas distributing means. A gas discharge duct communicates with a gas outlet adjacent to the gas distribution means opposite the magazine. The device is preferably used in the fabrication of semiconductor chips.

BACKGROUND OF THE INVENTION

a) Field of the Invention

The invention is directed to a device for transporting magazines holdingwafer-shaped objects formed of a magazine container which can bedeposited with its a releasable bottom and a depositing surface of itswall on a holding plate of an enclosure for a clean room, wherein theholding plate has a lowerable plate part supporting the bottom with thewafer magazine. The magazine container is a SMIF box whose use isfavored in the fabrication of semiconductor chips.

b) Description of the Related Art

Systems known as SMIF (Standard Mechanical Interface) systems contain aso-called SMIF box as a magazine container with an enclosed volume inwhich wafer magazines can be stored and transported. The SMIF box has areleasable bottom and is set down upon a holding plate of an enclosurefor a clean room in such a way that adhering dust particles are trappedbetween the bottom of the SMIF box and a plate part which can be loweredinto the clean room. The box itself surrounds the opening made in theenclosure.

A transport device of the type mentioned above is known, for instance,from U.S. Pat. No. 5,169,272.

Because of increasingly exacting demands for quality, a number ofprocess steps in semiconductor chip fabrication require that work becarded out within the enclosure in a gas atmosphere adapted to theproduction process. The quality of this gas atmosphere has a decisiveinfluence on the production results. In order to avoid disturbing thegas atmosphere when opening the box, it is necessary to produce withinthe box identical atmospheric conditions or a state in which the gasatmosphere is not influenced.

With the object of ensuring such adapted conditions, U.S. Pat. No.5,169,272 describes a process and a device which provide a stepwiselowering of the releasable bottom accompanied by generation of pressuredifferentials for the purpose of cleaning the SMIF box. The generatedpressure differential prevents gas from entering the clean room duringthe lowering process or while cleaning the SMIF box by means of guidinggas in the region of the bottom from one side of the SMIF box to theother.

A disadvantage in this solution consists in that the flow of gas throughthe interior of the box is incomplete, so that there is no assurancethat a required concentration gradient will be achieved within anacceptable time period.

On the other hand, high-temperature processes, for instance, requireremoval of oxygen. Since the nitrogen conventionally used for purging isheavier than the oxygen or oxygen-nitrogen mixture, an adequate changein the concentration of nitrogen to oxygen may not be possible. If thebox and magazine are purged with gas in an airlock, the consumption ofgas increases by a multiple and the purging time is substantiallyprolonged.

U.S. Pat. No. 4,724,874 provides a duct which connects the interiorregion of the SMIF box directly with an exterior region. A vacuum orover-pressure can be generated in the SMIF box and gas can betransported into the interior via the duct. This technical solution isnot suitable for carrying out an effective exchange of gas within theSMIF box. In spite of the high cost, a relatively long period of time isneeded to achieve a permissible residual concentration of harmful gas ina process gas.

Further, EP 273 226 A2 discloses a closable dust-tight transportcontainer with standardized outer dimensions whose semiconductor waferholder is arranged within the inner hood so as to be movable withoutfriction. Openings in an outer base plate and inner base plate and afilter element at the inner base plate serve to ensure particle-free airflow under fluctuating pressure ratios. Means serving only to compensatefor pressure are not suitable for generating within the transportcontainer a gas atmosphere adapted to the production process.

OBJECT AND SUMMARY OF THE INVENTION

The object of the present invention is to ensure an exchange of gaseswithin a SMIF box to the required extent at low cost and in an effectivemanner with respect to time in conformity to the working regimenassociated with an SMIF system.

According to the invention, by means of a device for transportingmagazines for holding wafer-shaped objects having a magazine containerwhich can be deposited, with a releasable bottom and a depositingsurface of its wall, on a holding plate of an enclosure for a cleanroom, wherein the holding plate has a lowerable plate part supportingthe bottom with the wafer magazine, this object is met in that a gasfeed duct proceeding from closable ducts incorporated in the wall opensinto means for distributing gas, and a gas discharge duct communicateswith a gas outlet adjacent to the gas distribution means opposite themagazine.

In the solution according to the invention, the gas exchange is carriedout to completion to a great extent by using a purging processdistributed along the entire interior region of the SMIF box, which gasexchange commences immediately after placement-of the SMIF box and isconcluded in the shortest possible time.

The means for distribution of gas are advantageously formed by adelivery strip which is removably fastened to the wall and tightlyconnected with the gas feed duct and in which are incorporated gasdistribution openings which are directed substantially to spaces betweenthe wafer-shaped objects and adjacent to the bottom and top surfaces ofthe magazine. The gas outlet is formed by a discharge strip which isremovably fastened to the wall, has gas discharge openings and istightly connected with the gas discharge duct. The ducts terminate atthe depositing surface in automatically closing valves which are openedwhen the magazine container is deposited by means of pipe piecesprojecting out of the holding plate so as to face the depositingsurface.

The pipe piece for opening the valve at the gas feed duct is connectedto a gas source and the pipe piece for opening the valve at the gasdischarge duct is connected to a vacuum. The gas exiting from the gassource and the connection to the vacuum are both regulated by a feelerwhich is actuated when the magazine is deposited.

Another advantage consists in that an enlarged flow-in space whoseboundaries are formed by angled portions of the wall and a diffuserwhich is arranged downstream of the flow-in space in the direction offlow and is fastened to the releasable bottom are provided as means forgas distribution and in that the gas outlet is formed by a gas dischargeduct which communicates with the interior of the magazine container viaan enlarged flow-out space formed by angled portions of the wall.

The gas feed duct and the gas discharge duct can be closed by means offlow-in valves actuated by gas pressure or can be provided with closingmeans which are actuated by linearly movable parts of coupling devicesprovided with openings for discharge and entry of gas.

The invention will be explained more fully in the following withreference to the schematic drawing.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:

FIG. 1 shows a simplified top view of a magazine container in the formof a SMIF box;

FIG. 2 shows first devices for gas feed in a deposited magazinecontainer;

FIG. 3 shows first devices for gas discharge in a deposited magazinecontainer;

FIG. 4 shows a deposited magazine container with second devices for gasfeed and gas discharge;

FIG. 5 shows the second devices for gas feed in an enlarged view;

FIG. 6 shows the second devices for gas discharge in an enlarged view;

FIG. 7 shows a deposited magazine container with third devices for gasfeed and gas discharge;

FIG. 8 shows the third devices for gas feed in an enlarged view; and

FIG. 9 shows the third devices for gas discharge in an enlarged view.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

While the foregoing description and drawings represent the preferredembodiments of the present invention, it will be obvious to thoseskilled in the art that various changes and modifications may be madetherein without departing from the true spirit and scope of the presentinvention.

As illustrated in FIG. 1, a magazine 3 for holding wafer-shaped objects,e.g., semiconductor wafers, is enclosed by the wall 2 of a magazinecontainer constructed as a SMIF box 1. A gas feed duct 4 (FIGS. 1 and 2)and a gas discharge duct 5 (FIGS. 1 and 2) are incorporated within thewall 2, their ends at a depositing surface 6 being provided withautomatically closing valves 7, 8 and enclosed by seals 9, 10 in theoutlet region leading to the interior of the container.

As further depicted in FIGS. 1 and 2 the seal 9 encloses a gas inletopening (not shown) of a delivery strip 11 by which the gas feed duct 4opens into gas distribution openings. For the purpose of cleaning theinterior of the container and the delivery strip 11 itself, the latteris fastened to holders 12 such that it may easily be detached. The gasdistribution openings are directed to spaces between wafer-shapedobjects and adjacent to the bottom and top surfaces of the magazine 3,these wafer-shaped objects being stored in the magazine 3 vertically toa movement direction Z.

As shown in FIGS. 1 and 3, the gas discharge duct 5 contacts a gasoutlet opening (not shown) of a discharge strip 13 via a seal 10 and isthus coupled with gas discharge openings 14 which adjoin the gasdistribution openings in the base region of the SMIF box opposite themagazine 3. The gas discharge openings 14 are structural components ofthe discharge strip 13 which, like the delivery strip 11, are easilydetached, i.e., can easily be removed from the SMIF box 1 withoutloosening connecting elements. Corresponding holders are designated by(FIG. 3) 15. The SMIF box 1 is deposited by a releasable bottom 16 andby the depositing surface 6 on a holding plate 17 which has a lowerableplate part 18. Miniature feelers 19 provided between the bottom 16 andplate part 18 serve to control the gas exiting from a gas source 20 andto actuate the valves for a vacuum connection. A pipe piece 21 whichfaces the depositing surface 6, projects out of the holding plate 17 andactuates the valve 7 is connected to the gas source 20. A seal 22provides for a tight connection. A filter 23 serves to clean the gasexiting from the gas source 20.

A pipe piece 24, shown in FIG. 3, which projects from the holding plate17 like pipe piece 21 and is enclosed by a seal 25 is provided foractuating the valve 8. The pipe piece 24 is connected to a vacuum via anelectromagnetic pneumatic valve 26.

In the deposited state of SMIF box 1, the bottom 16 rests on the platepart 18 and actuates the miniature feelers 19 whose signal opens anelectromagnetic pneumatic valve in the gas source 20 (FIG. 2) and thepneumatic valve 26 (FIG. 3). Consequently, gas which has been cleaned bythe filter 23 flows via the opened valve 7 and gas feed duct 4 into thedelivery strip 11 which distributes the gas via the gas distributionopenings such that the flow of gas is directed to the entire interiorregion of the SMIF box 1 and to the opposite side of the wall. In thisway, an effective exchange of gas is carried out within the entire SMIFbox 1.

The gas is discharged via the gas discharge openings 14, the gasdischarge duct 5, the opened valve 8 and the pipe piece 24.

When the SMIF box 1 is removed from the holding plate 17, valves 7 and 8are closed automatically. The pneumatic valves are closed either by thesignal generated by the miniature feelers 19 or by a signal producedwhen the plate part 16 is lowered, which means that the flow of gas isinterrupted when the SMIF box 1 is opened.

Another construction of the invention according to FIGS. 4 to 6 providesa SMIF box which is held laterally by guide rails 27 and is placed on aholding plate 28. A gas feed duct 31 (FIGS. 4 and 5) which can be closedby means of a flow-in valve 30 actuated by gas pressure is incorporatedin the wall 29 of this SMIF box at one side adjacent to the magazine 3.The gas feed duct 31 opens into gas distribution means whose componentparts include an enlarged flow-in space 32, whose boundaries are definedby angled portions of the wall 29, and a diffuser 34 which is arrangeddownstream of the flow-in space 32 and fastened to a releasable bottom33. Seals 35 provide for a tight connection.

A gas discharge duct 37 (FIGS. 4 and 6) which can be closed by aflow-out valve 36 which is also actuated by gas pressure is incorporatedin the wall 29 adjacent to the magazine 3 opposite the gas distributionmeans, this gas discharge duct 37 communicating with the interior of theSMIF box via an enlarged flow-out space 38 formed by angled portions ofthe wall 29.

As has already been described with respect to the construction accordingto FIGS. 1 and 2, pressure switches 40 (FIGS. 4 and 5) are actuated inthe deposited state of the SMIF box, in which the bottom 33 rests on alowerable plate part 39 of the holding plate 28, so that a signalgenerated by these pressure switches 40 opens electromagnetic pneumaticvalves 41, 42 in gas lines 43, 44.

Gas from a gas source (not shown) flows through the gas line 43, isfiltered by a filter 45 and arrives in the gas feed duct 31. The flow-invalve 30 is opened by the gas pressure and the gas flows into theflow-in space 32 in which it is deflected on the diffuser 34. Thediffuser 34 generates a uniform flow through the interior regions of theSMIF box and magazine located therein, preferably to the spaces betweensemiconductor wafers in the magazine 3 and adjacent to the bottom andtop surfaces. The gas passes through the gas discharge duct 37 into thegas line 44 via the flow-out space 38 and the flow-out valve 36 which isopened by vacuum pressure.

According to FIGS. 7 to 9, coupling devices 46, 47 are provided at theSMIF box for feeding and discharging gas, these coupling device 46, 47containing linearly movable parts 48, 49 which are provided withopenings 50, 51 for the inlet and outlet of gas and are suitable foropening closing means 52, 53 for a gas feed duct 54 and a gas dischargeduct 55.

The gas feed duct 54 (FIGS. 7 and 8) and gas discharge duct 55 (FIGS. 7and 9) are incorporated in the wall 56 adjacent to the magazine 3 onopposite sides. The closing means 52, 53 are pressed against sealingelements 59, 60 by spring elements 57, 58 so that the SMIF box is closedoutwardly without actuation of the coupling devices 46, 47.

Signals from pressure switches 61 which are actuated when the SMIF boxis deposited on a lowerable plate part 63 by its releasable bottom 62set the linearly movable pans 48, 49 in motion and open electromagneticpneumatic valves 64, 65. The gas flow cleaned by a filter 66 passes outof the opening 50 into the opened gas feed duct 54 via a gas line 67. Aflow-in space 68, a diffuser 69 and a flow-out space 70 act according tothe invention in the manner described with reference to FIGS. 4 to 6.Discharged gas exits the SMIF box via the opening 51 of the couplingdevice 47 and flows into gas line 71.

A guide rail is designated by 72, a holding plate is designated by 73and a box seal is designated by 74.

Cancellation of the coupled state which is necessary for a returningmovement of the movable parts 48, 49 is initiated by a feeler or switch(not shown) which can be actuated exclusively in the closed state of theSMIF box 1.

What is claimed is:
 1. A device for transporting magazines for holdingwafer-shaped objects, comprising:a magazine container having areleasable bottom wall and a side wall contiguous with said bottom wall,said side wall having a depositing surface engageable with a holdingplate of an enclosure for a clean room, where the holding plate has alowerable plate part, for supporting said bottom wall and a magazine insaid container; a gas feed duct disposed in said side wall andproceeding from closable ducts in said side wall; means for distributinggas, said gas feed duct opening into said means for distributing; and agas discharge duct communicating with a gas outlet adjacent to saidmeans for distributing opposite the magazine.
 2. The transport deviceaccording to claim 1, wherein the means for distribution of gas areformed by a delivery strip which is removably fastened to the wall andtightly connected with the gas feed duct and in which are incorporatedgas distribution openings which are directed substantially to spacesbetween the wafer-shaped objects and adjacent to the bottom and topsurfaces of the magazine, said gas outlet being formed by a dischargestrip which is removably fastened to the wall, has gas dischargeopenings and is tightly connected with the gas discharge duct, andwherein the ducts terminate at the depositing surface in automaticallyclosing valves which are opened when the magazine container is depositedby means of pipe pieces projecting out of the holding plate so as toface the depositing surface.
 3. The transport device according to claim2, wherein the pipe piece for opening the valve at the gas feed duct isconnected to a gas source, the gas entering from gas source beingregulated by a feeler which is actuated when the magazine is deposited.4. The transport device according to claim 3, wherein the pipe piece foropening the valve at the gas discharge duct is connected to a vacuum,said connection being regulated by a feeler which is actuated when themagazine is deposited.
 5. The transport device according to claim 1,wherein an enlarged flow-in space whose boundaries are formed by angledportions of the wall and a diffuser which is arranged downstream of theflow-in space in the direction of flow and is fastened to the releasablebottom are provided as means for gas distribution, and wherein the gasoutlet is formed by a gas discharge duct which communicates with theinterior of the magazine container via an enlarged flow-out space formedby angled portions of the wall.
 6. The transport device according toclaim 5, wherein the gas feed duct and the gas discharge duct can beclosed by means of flow-in valves which are actuated by gas pressure. 7.The transport device according to claim 5, wherein the gas feed duct andgas discharge duct are provided with closing means which are actuated bylinearly movable parts of coupling devices provided with openings forthe discharge and entry of gas.
 8. The transport device according toclaim 1, further comprising valves provided in said gas feed duct andsaid gas discharge duct, said valves including actuation means forautomatically opening said valves upon a placement of the device on theholding plate.
 9. The transport device according to claim 8 wherein saidactuation means includes means responsive to cooperating elementsoperatively coupled with the holding plate.
 10. The transport deviceaccording to claim 1 wherein said means for distributing gas includes adelivery strip removably fastened to said wall.
 11. A device fortransporting magazines for holding wafer-shaped objects, comprising:amagazine container having a releasable bottom wall and a side wallcontiguous with said bottom wall; a gas feed duct disposed in said sidewall; means in said container for distributing gas from said gas feedduct into said container; a gas discharge duct disposed in said sidewall on a side of said container opposite said gas feed duct; and valvemeans in said gas feed duct and said gas discharge duct forautomatically opening said gas feed duct and said gas discharge duct togas flow upon a deposition of said container on a holding plate of anenclosure for a clean room.
 12. The transport device according to claim11 wherein said means for distributing gas includes a delivery stripremovably fastened to said side wall.
 13. The transport device accordingto claim 12 wherein said delivery strip is provided with a plurality ofgas distribution openings which are directed in part to spaces betweenwafer-shaped objects in a magazine disposed in said container.